1. Field of the Invention
This invention relates to stir welding systems. More specifically, the invention is a method and system for weld nugget temperature control for thermal stir welding systems and processes.
2. Description of the Related Art
Stir welding is a form of welding that utilizes a small stir pin to mix abutting or faying surfaces of two pieces of material (e.g., metal materials) to thereby form a joint between the two pieces of material. There are several types of stir welding systems/processes. For example, thermal stir welding (TSW) is a solid-state welding process in which weld work pieces to be joined are heated (e.g., by an induction heater) and drawn by heavy forces between two containment plates applying compressive forces to the work pieces. The TSW stir pin is located between the containment plates and is rotated to create a join between the weld work pieces as they are drawn through the containment plates.
During a TSW process, the temperature of the stir pin has been used to control the power supplied to the induction heater to thereby control the temperature of the weld work pieces. However, the temperature of the stir pin is not necessarily the same as the temperature of the weld pieces. This is important for some materials that can only be welded if a tight temperature window is maintained at the weld (or in the “weld nugget” as it is also known). Furthermore, temperature of the weld nugget can also be affected by the rotational speed of the stir pin and the feed speed of the weld work pieces. Thus, just controlling a TSW system's heater may not provide the level of precise temperature control needed to produce good weld results.